The present disclosure relates to compositions that can be used to form conductive features and have a good shelf life prior to usage. Methods for making and using the same are also disclosed.
Organic thin-film transistors (OTFTs) can be used in applications such as radio frequency identification (RFID) tags and backplane switching circuits for displays, such as signage, readers, and liquid crystal displays, where high switching speeds and/or high density are not essential. They also have attractive mechanical properties such as being physically compact, lightweight, and flexible.
OTFTs are generally composed of, on a substrate, an electrically conductive gate electrode, source and drain electrodes, an electrically insulating gate dielectric layer which separate the gate electrode from the source and drain electrodes, and a semiconducting layer which is in contact with the gate dielectric layer and bridges the source and drain electrodes. Their performance can be determined by the field effect mobility and the current on/off ratio. High mobility and high on/off ratio are desired.
Both the mobility and on/off ratio are affected by the total resistance between the source and drain electrodes. If the total resistance is high, then high electrical field strengths are necessary to inject and extract charge carriers. One component of the total resistance is the contact resistance at the interface of each electrode and the semiconductor layer. Contact resistance is generally minimized by selecting an electrode material having a work function identical or very close to the energy level of the semiconductor. The energy level is the highest occupied molecular orbital (HOMO) of the semiconductor in the case of p-type semiconductor or the lowest unoccupied molecular orbital (LUMO) of the semiconductor in the case of n-type semiconductor.
For the electrodes, another key measure of performance is the conductivity. Generally, higher conductivity indicates better performance.
Organic thin-film transistors can be fabricated using low-cost solution-based patterning and deposition techniques, such as spin coating, solution casting, dip coating, stencil/screen printing, flexography, gravure, offset printing, ink jet-printing, micro-contact printing, and the like. To enable the use of these solution-based processes in fabricating thin-film transistor circuits, solution processable materials are therefore required.
It would be desirable to develop solution-processable compositions that exhibit good film-forming properties and can be used to form conductive features, such as electrodes.